Corrosive gases are frequently used for plasma etching in the manufacturing step of semiconductors, etc., and cleaning application of CVD devices. For these corrosive gases, fluorine based or chorine based gases, and the like are used. As the fluorine based gases, CF4, C2F6, C3F8, CHF3/CF4, SF6, and the like are used, and for the Cl based gases, Cl2, BCl3, CCl4, and the like are used. Further, it is also proposed to use HF, F2, or NF3.
In portions coming into contact with the above gases or plasma containing the gases, such as vessels, inner walls or parts, in which such corrosive gases are used, ceramics such as quartz, alumina, aluminum nitride, or metals such as aluminum or stainless steel are used. However, these members involved problems such that the member wastes away in a short period of time, and the member causes the generation of particles in the device.
For example, a quartz member reacts with a fluorine gas to form SiF4, which is then sublimated, and thus wastes away. Further, in ceramic members such as alumina or aluminum nitride, although a fluoride of aluminum, AlF3, is hardly sublimated, wastage occurs by physical sputtering or the like, and simultaneously corrosion selectively proceeds at the grain boundary or in pores of the member by plasma, whereby particles generate due to dropout of crystal particles.
As a method of solving these problems, a method is proposed, which suppresses the generation of particles by making the crystal grain boundary free and simultaneously introducing nitrogen to improve corrosion resistance, and it is proposed to use a glass constituted of Si—Al—O—N elements (see, for example, JP-A-11-228172). However, to produce such corrosion-resistant glasses, reducing atmosphere or inert atmosphere is required, resulting in a large scale of apparatus, and as a result, the corrosion-resistant member tends to be expensive. Further, such a composition is not always sufficient in corrosion resistance.
On the other hand, technologies for forming a sprayed coating on the surface of a base material protecting the base material are known, and it may be considered to form such a corrosion-resistant glass on a base material by spraying or coating. However, according to the conventional spraying technologies, the formation of a dense sprayed coating containing nitrogen has been difficult, and metals or oxide ceramics have mainly be used in the conventional formation of a protective film by spraying.
As the prior art technologies regarding formation of a sprayed coating containing nitrogen, for example, a method of forming an amorphous layer and YAG layer by spraying a mixed powder of AlN, SiO2 and MgO to Si3N4, Al2O3 or Y2O3 by explosive spraying (R. B. Heimann, S. Thiele, L. M. Berger, M. Herrmann, M. Nebelung, B. Wielage, T. M. Schnick and P. Vuoristo, “Thermally Sprayed Silicon Nitride-Based Coatings on Steel for Application in Severe Operation Environments: Preliminary Results”, Microstructural Science, vol. 26, 389 (1998); a method of forming a thermally sprayed silicon nitride coating by explosive spraying of β-SiAlON and χ-SiAlON powder obtained by heat treating a mixed powder of Si3N4, Al2O3, ZrO2 and TiO2; and a method of forming α-silicon nitride by plasma spraying of a mixed powder of Si3N4, Al2O3 and Y2O3 have been reported. However, since those sprayed coatings have high melting point, the sprayed powder which is not sufficiently melted deposits on a base material. As a result, bonding of mutual particles of the sprayed coating is weak, and the number of pores increases, resulting in decrease of density. Consequently, corrosion selectively proceeds at the grain boundary or in pores of the member in plasma etching, whereby particles tend to generate due to dropout of crystal particles. Further, durability of the sprayed coating to corrosive gases or plasma has not been sufficient. In addition, an apparatus used in explosion spraying is expensive, deposition efficiency of the sprayed coating is poor, and a metal base material such as aluminum may deform by wind pressure at explosion.
Thus, the technology of producing a dense sprayed coating containing nitrogen having good bonding of particles with each other and also being provided with very high corrosion resistance, using the conventional spraying method has conventionally required further improvement, and a corrosion-resistant member which does not cause generation of particles due to dropout of crystal particles during plasma etching and has good corrosion resistance to corrosive gases or plasma has been demanded.
As described above, in the step of using corrosive gases or plasma in a semiconductor production process, there have been the problems of particle generation due to corrosion of a member, contamination of a product due to such generation, gain decrease, and the like. There has been further problem of decrease in life of a member due to low corrosion resistance of the member. A vitreous corrosion-resistant member constituted of Si—Al—O—N elements for the purpose of suppressing this problem has been proposed. However, such a member has not always sufficient in corrosion resistance. On the other hand, spraying with Si3N4—Al2O3—Y2O3 system is possible, but the sprayed coating has low density. Further, it is necessary to solve the problem of particle generation.